NH3 is the HRC code for the NSR250 Formula 3. An example would be that all NSR250 engines are stamped MC16, whereas the F3 HRC engines are stamped NH3. Which basically means it's a very special part, with lots of equally special parts inside.
StephenRC45 will turn his nose up at most boring KV3 (standard NSR250) parts, but show him anything with NH3 on it and he goes wobbly at the knees
Oh by the way Steve, when I got home last night I found another NH3 water pump cover
Most of the NH3 parts are heavily based on the NF5 parts, and because of this a good F3 engine will make very similar horse power to a (same era) RS250. Maybe just a couple of horse shy becuase of a couple of design flaws that HRC kept in the NSR engine to stop it beating the RS. That's my opinion.
To wrap up, NH3 stuff for the NSR is as good as it gets. Well, from HRC anyway. It's good, but it could be better
